Improve and fix some error handling for REINDEX INDEX/TABLE CONCURRENTLY

This improves the user experience when it comes to restrict several
flavors of REINDEX CONCURRENTLY.  First, for INDEX, remove a restriction
on shared relations as we already check after catalog relations.  Then,
for TABLE, add a proper error message when attempting to run the command
on system catalogs.  The code path of CREATE INDEX CONCURRENTLY already
complains about that, but if a REINDEX is issued then then the error
generated is confusing.

While on it, add more tests to check restrictions on catalog indexes and
on toast table/index for catalogs.  Some error messages are improved,
with wording suggestion coming from Tom Lane.

Reported-by: Tom Lane
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/23694.1556806002@sss.pgh.pa.us

Author: michaelpq

src/backend/commands/indexcmds.c

@@ -2743,6 +2743,12 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 
 				MemoryContextSwitchTo(oldcontext);
 
+				/* A system catalog cannot be reindexed concurrently */
+				if (IsCatalogRelationOid(relationOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("cannot reindex a system catalog concurrently")));
+
 				/* Open relation to get its indexes */
 				heapRelation = table_open(relationOid, ShareUpdateExclusiveLock);
 
@@ -2756,13 +2762,13 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 					if (!indexRelation->rd_index->indisvalid)
 						ereport(WARNING,
 								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-								 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+								 errmsg("cannot reindex invalid index \"%s.%s\" concurrently, skipping",
 										get_namespace_name(get_rel_namespace(cellOid)),
 										get_rel_name(cellOid))));
 					else if (indexRelation->rd_index->indisexclusion)
 						ereport(WARNING,
 								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-								 errmsg("cannot reindex concurrently exclusion constraint index \"%s.%s\", skipping",
+								 errmsg("cannot reindex exclusion constraint index \"%s.%s\" concurrently, skipping",
 										get_namespace_name(get_rel_namespace(cellOid)),
 										get_rel_name(cellOid))));
 					else
@@ -2802,7 +2808,7 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 						if (!indexRelation->rd_index->indisvalid)
 							ereport(WARNING,
 									(errcode(ERRCODE_INDEX_CORRUPTED),
-									 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+									 errmsg("cannot reindex invalid index \"%s.%s\" concurrently, skipping",
 											get_namespace_name(get_rel_namespace(cellOid)),
 											get_rel_name(cellOid))));
 						else
@@ -2831,17 +2837,11 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 			{
 				Oid			heapId = IndexGetRelation(relationOid, false);
 
-				/* A shared relation cannot be reindexed concurrently */
-				if (IsSharedRelation(heapId))
-					ereport(ERROR,
-							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("concurrent reindex is not supported for shared relations")));
-
 				/* A system catalog cannot be reindexed concurrently */
 				if (IsCatalogRelationOid(heapId))
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("concurrent reindex is not supported for catalog relations")));
+							 errmsg("cannot reindex a system catalog concurrently")));
 
 				/* Save the list of relation OIDs in private context */
 				oldcontext = MemoryContextSwitchTo(private_context);
@@ -2869,7 +2869,7 @@ ReindexRelationConcurrently(Oid relationOid, int options)
 			/* Return error if type of relation is not supported */
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("cannot reindex concurrently this type of relation")));
+					 errmsg("cannot reindex this type of relation concurrently")));
 			break;
 	}
 

src/test/regress/expected/create_index.out

@@ -1967,7 +1967,7 @@ INSERT INTO concur_reindex_tab3 VALUES  (3, '[1,2]');
 REINDEX INDEX CONCURRENTLY  concur_reindex_tab3_c2_excl;  -- error
 ERROR:  concurrent index creation for exclusion constraints is not supported
 REINDEX TABLE CONCURRENTLY concur_reindex_tab3;  -- succeeds with warning
-WARNING:  cannot reindex concurrently exclusion constraint index "public.concur_reindex_tab3_c2_excl", skipping
+WARNING:  cannot reindex exclusion constraint index "public.concur_reindex_tab3_c2_excl" concurrently, skipping
 INSERT INTO concur_reindex_tab3 VALUES  (4, '[2,4]');
 ERROR:  conflicting key value violates exclusion constraint "concur_reindex_tab3_c2_excl"
 DETAIL:  Key (c2)=([2,5)) conflicts with existing key (c2)=([1,3)).
@@ -2092,10 +2092,15 @@ BEGIN;
 REINDEX TABLE CONCURRENTLY concur_reindex_tab;
 ERROR:  REINDEX CONCURRENTLY cannot run inside a transaction block
 COMMIT;
-REINDEX TABLE CONCURRENTLY pg_database; -- no shared relation
-ERROR:  concurrent index creation on system catalog tables is not supported
-REINDEX TABLE CONCURRENTLY pg_class; -- no catalog relations
-ERROR:  concurrent index creation on system catalog tables is not supported
+REINDEX TABLE CONCURRENTLY pg_class; -- no catalog relation
+ERROR:  cannot reindex a system catalog concurrently
+REINDEX INDEX CONCURRENTLY pg_class_oid_index; -- no catalog index
+ERROR:  cannot reindex a system catalog concurrently
+-- These are the toast table and index of pg_authid.
+REINDEX TABLE CONCURRENTLY pg_toast.pg_toast_1260; -- no catalog toast table
+ERROR:  cannot reindex a system catalog concurrently
+REINDEX INDEX CONCURRENTLY pg_toast.pg_toast_1260_index; -- no catalog toast index
+ERROR:  cannot reindex a system catalog concurrently
 REINDEX SYSTEM CONCURRENTLY postgres; -- not allowed for SYSTEM
 ERROR:  concurrent reindex of system catalogs is not supported
 -- Warns about catalog relations
@@ -2144,7 +2149,7 @@ DROP INDEX concur_reindex_ind5_ccnew;
 DELETE FROM concur_reindex_tab4 WHERE c1 = 1;
 -- The invalid index is not processed when running REINDEX TABLE.
 REINDEX TABLE CONCURRENTLY concur_reindex_tab4;
-WARNING:  cannot reindex concurrently invalid index "public.concur_reindex_ind5", skipping
+WARNING:  cannot reindex invalid index "public.concur_reindex_ind5" concurrently, skipping
 NOTICE:  table "concur_reindex_tab4" has no indexes
 \d concur_reindex_tab4
         Table "public.concur_reindex_tab4"

src/test/regress/sql/create_index.sql

@@ -838,8 +838,11 @@ DROP TABLE concur_reindex_part;
 BEGIN;
 REINDEX TABLE CONCURRENTLY concur_reindex_tab;
 COMMIT;
-REINDEX TABLE CONCURRENTLY pg_database; -- no shared relation
-REINDEX TABLE CONCURRENTLY pg_class; -- no catalog relations
+REINDEX TABLE CONCURRENTLY pg_class; -- no catalog relation
+REINDEX INDEX CONCURRENTLY pg_class_oid_index; -- no catalog index
+-- These are the toast table and index of pg_authid.
+REINDEX TABLE CONCURRENTLY pg_toast.pg_toast_1260; -- no catalog toast table
+REINDEX INDEX CONCURRENTLY pg_toast.pg_toast_1260_index; -- no catalog toast index
 REINDEX SYSTEM CONCURRENTLY postgres; -- not allowed for SYSTEM
 -- Warns about catalog relations
 REINDEX SCHEMA CONCURRENTLY pg_catalog;